I don't know the history or timing of it well at all, but it was precisely calculated from experiment with the constant x m1 x m2 / d^2 thing, I believe. I assume that was around for a 100+ years, and I think it wasn't derived from theory of globe earth but to explain Keplers 3 thingies...which I'm not sure about the timing of (maybe Kepler was post globe earth...). Looking to you to educate me, as I've got important things to do!

I don't know about Kepler but wasn't Cavendish the first recorded person to measure gravity? in like the 17th century? but I think that was just that mass generally has gravity, ie distorts spacetime (he didn't call it that of course) not the local gravitational acceleration of the Earth. I think Newton generally measured that. and a bunch of people also at the end of the 17th century refined the actual measurement. (and they also noticed that it was *different* at different elevations, destroying my guys "gravity is an inertial force due to upward acceleration" hypothesis)